Water Color Odor Appearance and Taste
Your First Evidence of a Problem
Secondary Water Quality Issues
COLOR
Is your water safe to drink? Does it smell funny or is it cloudy or off-color?
The increase in the reported cases of chemical spills, leaking oil tanks, toxic waste sites, and pesticide
use may make you wonder about the quality and safety of your water. what is in your water. Whether you get your water from a
public or a privately-owned public water system, or your own well or spring, having a safe
source of drinking water is vital to the health of you and your family.
Changes in the appearance, taste, odor, and color may be your first evidence of
a problem. Color in water can be caused by a number of contaminants such as iron
which changes in the presence of oxygen to yellow or red sediment. Color
from iron is referred to as "apparent color" rather than "true color".
True color is distinguished from apparent color by filtering the sample.
The most common source of true color is decaying organic matter such
as the yellowish "tea color" of water in tundra or wet bogs. True color
is mostly found in surface water, although ground water may contain some
color if the aquifer flows through a layer of buried vegetation, such as
from a long buried slough of a river.
Color is not a toxic characteristic, but is listed by the EPA
as a
secondary (aesthetic) parameter affecting the appearance and palatability
of the water. When chlorinated, color-causing organic matter may form
chlorinated organic compounds such as trihalomethanes. Chloroform is a
common trihalomethane, and is along with several others, considered to be
a potential carcinogen. For this reason ADEC limits total
trihalomethanes (TTHM's) in public water supplies to 0.1 ppm (100 ppb).
Color is measured in units based on a platinum-cobalt standard solution
which forms a yellow tint and is limited to 15 units in public water
supplies.
Color can be removed by activated carbon filters,
sometimes marketed as taste and odor filters. The activated carbon or
charcoal must be replaced after a period of time when its capacity for
adsorption of the color is exhausted. Another treatment method is
coagulation and sedimentation using alum or other chemicals. This
process is normally used only in large plants since its complexity
requires the care of a trained water treatment plant operator.
Color analysis is done by visual comparison to a set of
platinum-cobalt standards in Nessler tubes. Sample collection is done in
a clean rinsed bottle which should be refrigerated if stored for more
than a few hours.
If the color of the water exceeds 15 color units and the water is being
chlorinated, we suggest having the water examined for total
trihalomethanes by gas chromatography. This is a more expensive and time
consuming analysis, but is extremely sensitive with detection limits
down to the ppb level. Sample vials specially designed to eliminate the
air space above the sample are required for sampling. For laboratory
testing for organics and other chemicals, please visit the
Drinking Water Testing Website.
